
224 “Report OF THE Cems ¢ OF THE 
or minute germs, or, as we etonly say, itferments, forming, as _ 
one of its chief products, lactic acid, the characteristic acid of - 
sour milk. The sugar, in the process of cheese-making, passes 
mostly into the whey. In some few places, the milk sugar is 
obtained from the whey and converted into an article of commerce, 
for which there is a limited demand, but, in most cases, no attempt 
is made to recover it. The amount of sugar in milk averages not 
far from five pounds per hundred. 
(3) The Ash in milk consists of what is left after milk is 
burned as completely as possible. It contains compounds made 
up of such elements as calcium, phosphorus, potassium, sodium, 
magnesium, oxygen, sulphur, chlorine, iron, ete. A large part of 
the ash-constituents is lost in the whey. The average amount 
of ash in milk is about three-fourths of one pound per hundred 
pounds of milk. The calcium (or lime) compounds in milk are of 
especial importance in connection with the process of cheese- 
making, since it has been recently shown that rennet will not 
coagulate the casein of milk unless some soluble calciwm compound 
is present, though it is not clearly understood in exactly what 
way the calcium compounds influence the action of rennet. 
The following table will give a fair idea of the average 
composition of normal milk : 
Pounds per 
hundred. 
VELEN Gites. hee Be age ee oe Ts PONE NaS ooh ul Ge Ae 87.2 
POCA) BOLIAS. 9) OU sian ea far bibs pee Warn a wine le sv 5%e re 12.8 
Habre. coli See eae Teena Co, ESR eee <3 aes 3:8 
Solids: notifatiiciys 2. aReae .) Ce eited been nes. cine oe 920 
Casein and albumen ........... Sha a iO va. o) te ance eh chats 3.3 
{reds Pee es," > Rae IAL IIG aR REY Bs <\a\'») adam he ce 5.0 
Aghit cage uum ‘> | RE ee Lito wane eh iota sles eS ee 0.7 
ACTION OF RENNET UPON THE CASEIN OF MILK. 
The action of rennet in coagulating the casein of milk is due to 
a chemical ferment contained in the rennet. This ferment, when 
introduced into milk, acts at certain temperatures with great 
rapidity, and produces marked changes, chief among which is the 
coagulation or solidification of- the casein. The exact chemical | 
changes produced in casein by its coagulation are not satisfactorily 
See ee ee a. 
aS ee ee eS ee a 
a, 

